Phase 1/2 Trial of Carfilzomib Plus High-Dose Melphalan Preparative Regimen for Salvage Autologous Hematopoietic Cell Transplantation Followed by Maintenance Carfilzomib in Patients with Relapsed/Refractory Multiple Myeloma

Busulfan, melphalan and carfilzomib high-dose chemotherapy and autologous haematopoietic stem cell transplantation in multiple myeloma

The standard of care for fit, newly diagnosed multiple myeloma patients includes induction therapy followed by consolidative high-dose chemotherapy with melphalan and autologous stem cell transplant (AHSCT). Intensified preparative regimens, such as busulfan and melphalan (BuMel), have shown promise to lengthen progression-free survival (PFS). We previously reported that the addition of bortezomib to BuMel improved PFS compared to melphalan alone in CIBMTR-matched controls. We now integrate the second-generation protease inhibitor, carfilzomib, before and after BuMel (BuMelCar) in a phase I/II trial with carfilzomib. Patients with NDMM, relapsed/refractory MM (RRMM) and those failing prior AHSCT were eligible. Primary end-points were safety and tolerability. Secondary end-points included minimal residual disease negativity rates, PFS and OS. The study enrolled 19 patients. 73% were high risk either due to R-ISS III status, adverse genetics or relapsed after prior AHSCT. The maximum tolerated dose (MTD) of carfilzomib was determined to be 36 mg/m2. Noted grade 3 toxicities were febrile neutropenia (79%), mucositis (21%) and diarrhoea (16%). The 2-year PFS for the whole cohort and MTD was 89% and 100% respectively. 80% of all patients and 82% of patients in the MTD cohort achieved MRD negativity. Further studies regarding this regimen are planned.

Optimizing high dose melphalan

Melphalan, has been a major component of myeloma therapy since the 1950s. In the context of hematopoietic cell transplantation (HCT), high dose melphalan (HDM) is the most common conditioning regimen used due to its potent anti-myeloma effects and manageable toxicities. Common toxicities associated with HDM include myelosuppression, gastrointestinal issues, and mucositis. Established approaches to reduce these toxicities encompass dose modification, nausea prophylaxis with 5HT3 receptor antagonists, cryotherapy, amifostine use, and growth factors. Optimization of melphalan exposure through personalized dosing and its combination with other agents like busulfan, or bendamustine show promise. Propylene glycol-free melphalan (Evomela) represents a novel formulation aiming to enhance drug stability and reduce adverse effects. This review explores strategies to enhance the efficacy and mitigate the toxicity of HDM in multiple myeloma. Future directions involve exploring these strategies in clinical trials to improve the safety and efficacy of HDM, thereby enhancing outcomes for multiple myeloma patients undergoing autologous HCT.

Trends in utilization of stored cryopreserved autologous peripheral hematopoietic cells intended for a second (or beyond) autologous hematopoietic cell transplantation in patients with multiple myeloma: a single center experience

Due to the advent of effective novel therapies for multiple myeloma (MM), the use of cryopreserved autologous peripheral blood hematopoietic cells (APBHC) for a salvage autologous transplant (auto-HCT) is in decline. We evaluated utilization trends and costs associated with cryopreserved APBHC in patients with MM. We retrospectively evaluated the clinicopathologic data from 440 patients with MM who underwent APBHC mobilization and collection at Mayo Clinic Florida between 2010 and 2019. Based on institution-specific charges as of May 2021, the cost of 1 session of APBHC collection/apheresis was $4,680 and the cost of 1 year of APBHC cryopreservation was $4,790 per patient. Out of 347 patients who had APBHC in cryopreservation, 5 (1.4%) underwent a salvage auto-HCT and 61% of patients had ≥1 excess collection sessions for APBHC that ultimately went unused. The median cost of excess collection sessions was $4,680 per patient (range, $4,680-$32,760) and the median total cost for excess collection sessions plus costs for storage was $23,840 per patient (range, $4,680-$85,450). The sum of costs of excess collection sessions was $2,077,920 and the sum of costs of cryopreservation was $5,812,665. Institutional policies regarding universal APBHC collection and long-term storage should be reevaluated in the era of novel therapeutics.

Proteasome inhibition in combination with immunotherapies: State-of-the-Art in multiple myeloma

Multiple myeloma (MM) is a malignant plasma cell disorder accounting for around 1.8% of all neoplastic diseases. Nowadays, clinicians have a broad arsenal of drugs at their disposal for the treatment of MM, such as proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, bispecific antibodies, CAR T-cell therapies and antibody-drug conjugates. In this paper we briefly highlight essential clinical elements relating to proteasome inhibitors, such as bortezomib, carfilzomib and ixazomib. Studies suggest that the early use of immunotherapy may improve outcomes significantly. Therefore, in our review we specifically focus on the combination therapy of proteasome inhibitors with novel immunotherapies and/or transplant. A high number of patients develop PI resistance. Thus, we also review new generation PIs, such as marizomib, oprozomib (ONX0912) and delanzomib (CEP-18770) and their combinations with immunotherapies.

A phase 1/2 of carfilzomib and melphalan conditioning for autologous stem cell transplantation for multiple myeloma (CARAMEL)

In this phase 1/2 study, carfilzomib was added to high-dose melphalan conditioning prior to autologous stem cell transplantation (ASCT) in patients with multiple myeloma that had been treated with ≤2 prior lines of therapy. Carfilzomib was escalated at doses of 27, 36, 45, and 56 mg/m2 on days -6, -5, -2, and -1 before ASCT in the phase 1 component of the study. In addition, all the patients received melphalan 100 mg/m2 on days -4 and -3. The primary endpoint of the phase 1 component was to identify the maximum tolerated dose, and the primary endpoint of the phase 2 component was the rates of complete response (≥CR) at 1 year after ASCT. The phase 1 dose escalation cohort included 14 patients, and 35 patients were included in the phase 2 cohort. The maximum tested dose was 56 mg/m2 (MTD). The median time from diagnosis to study enrollment was 5.8 (range 3.4-88.4) months, and 16% of patients had obtained a ≥CR prior to ASCT. The best response within 1 year after ASCT was a ≥ CR rate in 22% for the entire cohort, and 22% for patients treated at the MTD. The ≥VGPR rates improved from 41% before ASCT to 77% by 1 year after ASCT. One patient had a grade 3 renal adverse event, and renal function returned to baseline with supportive care. The rate of grade 3-4 cardiovascular toxicity was 16%. The addition of carfilzomib to melphalan conditioning was safe and resulted in deep responses after ASCT.

Bortezomib and high-dose melphalan conditioning regimen in frontline multiple myeloma: an IFM randomized phase 3 study

High-dose melphalan (HDM) and transplantation are recommended for eligible patients with multiple myeloma. No other conditioning regimen has proven to be more effective and/or safer. We previously reported in a phase 2 study that bortezomib can safely and effectively be combined with HDM (Bor-HDM), with a 32% complete response (CR) rate after transplantation. These data supported a randomized phase 3 trial. Randomization was stratified according to risk and response to induction: 300 patients were enrolled, and 154 were allocated to the experimental arm (ie, arm A) with bortezomib (1 mg/m2 intravenously [IV]) on days -6, -3, +1, and +4 and melphalan (200 mg/m2 IV) on day -2. The control arm (ie, arm B) consisted of HDM alone (200 mg/m2 IV). There were no differences in stringent CR + CR rates at day 60 posttransplant (primary end point): 22.1% in arm A vs 20.5% in arm B (P = .844). There were also no differences in undetectable minimum residual disease rates: 41.3% vs 39.4% (P = .864). Median progression-free survival was 34.0 months for arm A vs 29.6 months for arm B (adjusted HR, 0.82; 95% CI, 0.61-1.13; P = .244). The estimated 3-year overall survival was 89.5% in both arms (hazard ratio, 1.28; 95% CI, 0.62-2.64; P = .374). Sixty-nine serious adverse events occurred in 18.7% of Bor-HDM-treated patients (vs 13.1% in HDM-treated patients). The proportion of grade 3/4 AEs was similar within the 2 groups (72.0% vs 73.1%), mainly (as expected) blood and gastrointestinal disorders; 4% of patients reported grade 3/4 or painful peripheral neuropathy in arm A (vs 1.5% in arm B). In this randomized phase 3 study, a conditioning regimen with Bor-HDM did not improve efficacy end points or outcomes compared with HDM alone. The original trial was registered at www.clinicaltrials.gov as #NCT02197221.

Carfilzomib and dexamethasone maintenance following salvage ASCT in multiple myeloma: A randomised phase 2 trial by the Nordic Myeloma Study Group

Objective

We investigated the efficacy and safety of carfilzomib‐containing induction before salvage high‐dose melphalan with autologous stem‐cell transplantation (salvage ASCT) and maintenance with carfilzomib and dexamethasone after salvage ASCT in multiple myeloma.

Methods

This randomised, open‐label, phase 2 trial included patients with first relapse of multiple myeloma after upfront ASCT who were re‐induced with four cycles of carfilzomib, cyclophosphamide and dexamethasone. Two months after salvage, ASCT patients were randomised to either observation or maintenance therapy with iv carfilzomib 27 → 56 mg/sqm and p.o. dexamethasone 20 mg every second week. The study enrolled 200 patients of which 168 were randomised to either maintenance with carfilzomib and dexamethasone (n = 82) or observation (n = 86).

Results

Median time to progression (TTP) after randomisation was 25.1 months (22.5‐NR) in the carfilzomib‐dexamethasone maintenance group and 16.7 months (14.4–21.8) in the control group (HR 0.46, 95% CI 0.30–0.71; P = .0004). The most common adverse events during maintenance were thrombocytopenia, anaemia, hypertension, dyspnoea and bacterial infections.

Conclusion

In summary, maintenance therapy with carfilzomib and dexamethasone after salvage ASCT prolonged TTP with 8 months. The maintenance treatment was in general well‐tolerated with manageable toxicity.

Retrospective Study of Carfilzomib-Pomalidomide-Dexamethasone in Relapsed/Refractory Multiple Myeloma Patients in a Tertiary Care Hospital in India

Carfilzomib is a second-in class Proteosome Inhibitor and has been approved for Relapsed/Refractory Multiple Myeloma (RRMM). We retrospectively retrieved and analyzed data of KPd combination both biweekly and weekly regimens at our centre from 1 st August 2017 and 31 st May 2020. Sixty-nine patients were treated with KPd with median age of 58 years. Median prior lines of chemotherapy were 2(1-15). Twenty-eight (40.5%) patients underwent autoSCT. Median no. of cycles was 4(1-12) and 3(1-13) with median time to response of 4(2-12) and 2(2-6) months in biweekly and once weekly regimen cohorts respectively. At last follow-up, overall response rate (ORR) was 65.2%{CR-n = 10 (14.5%), VGPR-n = 19 (27.5%), PR-n = 16 (23.2%)} with n = 13(18.8%) patients had PD and relapse was observed in n = 24(34.8%). Thirty (43.4%) patients received maintenance therapy {n = 21(70%)} or autoSCT {n = 9(30%)}. Common toxicities were anemia {n = 11(15.9 %)}, thrombocytopenia (n = 15(21.7%) and neutropenia (n = 16 (23.2%)}, hypertension {n = 28(40.5%)}, peripheral neuropathy (grade1/2) {n = 15(21.7%)}, infections [n = 18(26%) {bacterial [n = 9(13%),viral n = 7(10.1%), fungal n = 8(11.6%)}]. At a median follow-up of 18 months, the estimated median PFS was 11.3 months (95%C.I. 8.3– 14.2) whereas the estimated median OS was 28 months (95%C.I. 20.4-35.5) for the entire cohort. Mortality rate of 2.5% and 10% in two cohorts respectively. Commonest cause of death was PD and sepsis. KPD is a well-tolerated regimen for RRMM, which can be a bridge to ASCT, however with significant side effects.

Outcomes after delayed and second autologous stem cell transplant in patients with relapsed multiple myeloma

We evaluated the outcomes of 168 patients undergoing delayed or second autologous stem cell transplant (ASCT) for relapsed multiple myeloma (MM) from 2010 to 2019. Overall, 21% (n = 35) patients had received a prior transplant and 69% (n = 116) underwent transplant at first relapse. Overall, 27% patients had high-risk cytogenetics and 15% had ISS stage III disease. Stem cell collection was performed after relapse in 72% and 35% of patients received maintenance therapy. Median PFS from salvage treatment and transplant were 28 and 19 months, respectively. Median OS from salvage treatment and transplant was 69 and 55 months. Multivariate analysis revealed that ASCT in first relapse was associated with superior PFS (HR 0.63, p = 0.03) and OS (HR 0.59, p = 0.04) compared to later lines of therapy. In addition, PFS of ≥36 months with prior therapy was associated with improved PFS (HR 0.62, p = 0.04) and OS (HR 0.41, p = 0.01). Ninety-five patients underwent delayed transplant at first relapse, median PFS and OS from start of therapy was 30 and 69 months, and median OS from diagnosis was 106 months. These data may serve as a guide when counseling patients undergoing ASCT for relapsed MM and provide a benchmark in designing clinical trials of transplantation/comparative treatments for relapsed MM.

Future Directions in Maintenance Therapy in Multiple Myeloma

Autologous stem cell transplantation (ASCT) has been a backbone of therapy for newly diagnosed patients with multiple myeloma eligible for high-dose therapy for decades. Survival outcomes have continued to improve over time, in part because of the incorporation of highly effective induction regimens prior to ASCT as well as post-ASCT maintenance therapy. Randomized phase III clinical trials have helped establish lenalidomide maintenance as a standard of care. However, as nearly all patients will eventually experience disease relapse, there continues to be significant interest in developing novel maintenance strategies to improve upon lenalidomide maintenance. In this review, we summarize the available evidence for the use of immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies as post-ASCT maintenance therapies as well as discuss future directions and unanswered questions in the field.

Post-Transplant Maintenance Treatment Options in Multiple Myeloma

Maintenance therapy post autologous stem cell transplant (ASCT) is commonly employed in myeloma patients to prolong remission, as relapse invariably occurs after ASCT. After initial diagnosis and risk stratification, patients receive initial therapy with a combination of drugs, typically a proteasome inhibitor and an immunomodulatory imide drug (IMiD), and in those considered eligible, high-dose chemotherapy followed by autologous stem cell transplant. The aim of our study was to review the literature and consolidate evidence regarding different maintenance therapies post stem cell transplant in myeloma patients. We reviewed major databases including PubMed, Cochrane Library and Evidence-Based Medicine Reviews (EBMR), along with American Society of Hematology/American Society of Clinical Oncology (ASH/ASCO) conference abstracts to include relevant literature. Ongoing clinical trials were also reviewed. Consolidation therapy is often employed to enhance the response to induction therapy and SCT and also to delay progression. Melphalan and thalidomide with or without steroids were initially used as maintenance therapy. More recently, lenalidomide-, bortezomib-, ixazomib-, or carfilzomib-based regimens have been employed as maintenance. Lenalidomide and bortezomib are the most commonly used drugs, with the latter being preferred in high-risk populations. Newer trials are utilizing tumor-specific antigen based vaccines along with adoptive T-cell therapies, and monoclonal antibodies as maintenance therapy. We conclude that maintenance therapy post SCT, with lenalidomide or bortezomib is the standard of care in myeloma patients. Patient tolerability, disease risk stratification and prior therapy received are major determinants of the choice of maintenance. Significant toxicity associated with maintenance therapies is a hindrance to long-term maintenance post stem cell transplant.

Utilization and Cost Implications of Hematopoietic Progenitor Cells Stored for a Future Salvage Autologous Transplantation or Stem Cell Boost in Myeloma Patients

Autologous hematopoietic cell transplantation (autoHCT) is a standard initial treatment for multiple myeloma (MM). Consensus guidelines recommend collecting sufficient hematopoietic progenitor cells (HPCs) for 2 autoHCTs in all eligible patients. Despite a lack of published data on the utilization of HPCs stored for future use, it is common practice across transplantation programs to collect enough HPCs for 2 autoHCTs in MM patients. In this single-center retrospective study, we analyzed the utilization of HPCs collected and stored at the time of first autoHCT in patients with MM, along with the cost implications of HPC collection targets sufficient for 2 transplantations. In a cohort of 400 patients (median age, 63 years; range, 22 to 79 years), after a median follow-up of 50.4 months, 197 patients had relapsed and 36 had received HPC infusion as salvage autoHCT (n = 29) and/or HPC boost (n = 8). In this cohort, a median CD34⁺ cell dose of 4.3 × 10⁶/kg (range, 1.1 to 12.94.3 × 10⁶/kg) was used for first autoHCT, and a median of 4.4 × 10⁶/kg (range, 1.0 to 20.2× 10⁶/kg) CD34⁺ cells were stored for future use. At 6 years after the first autoHCT, the estimated cumulative incidence of salvage autoHCT was 12.0% without HPC boost and 13.9% with HPC boost. HPC utilization was significantly higher in the 60- to 64-year age group, whereas no patients who were age ≥70 years at the time of first autoHCT received salvage autoHCT. Using the CD34⁺ cell dose infused during the first autoHCT as the cutoff for individual patients, the estimated mean additional cost of HPC collection intended for subsequent use (over and above the HPCs used for first autoHCT) was $10,795 ($4.32 million for the entire cohort), an estimated 14% of which (ie, $583,600) was actually used up in salvage autoHCT by 6 years from first autoHCT. In conclusion, our results suggest the need for reappraisal of HPC collection targets for salvage autoHCT and argue against HPC collection and storage for salvage autoHCT in patients age ≥70 years at the time of first autoHCT.

High-dose bendamustine and melphalan conditioning for autologous stem cell transplantation for patients with multiple myeloma

High-dose melphalan (MEL200) followed by autologous stem cell transplantation (ASCT) remains a standard of care for multiple myeloma (MM). Bendamustine induces responses in MM resistant to other alkylators. Our prior Phase I trial adding bendamustine to MEL200 transplant conditioning resulted in no additional toxicity. We now report a single-arm, phase II study that evaluated the efficacy of bendamustine 225 mg/m² with MEL200 conditioning for ASCT in 18 patients with newly diagnosed MM (NDMM) and 17 with relapsed or refractory MM (RRMM). The primary end point was the complete response (CR/sCR) rate at day+ 100. Sample size was determined according to Simon's two-stage design. At stage 1, sixteen patients entered the study. As there were eight patients with CR/sCR, enrollment increased to 28 patients. Sixteen out of the first 28 evaluable patients achieved CR/sCR, meeting the design criteria. Enrollment was then expanded to a total of 35 patients. 51% achieved a CR/sCR. After a median follow-up of 65 months, 21 patients progressed, including 7 deaths. The median PFS for NDMM and RRMM was 48 and 45 months, respectively. Bendamustine/MEL200 conditioning resulted in excellent overall and depth of response as well as PFS, particularly in the RRMM patients, and is worthy of further investigation (NCT00916058).

A phase I/II study of escalating doses of thalidomide in conjunction with bortezomib and high-dose melphalan as a conditioning regimen for autologous stem cell transplantation in patients with multiple myeloma

A regimen of escalating doses of thalidomide, in combination with bortezomib and high-dose melphalan (mel/vel/thal), was evaluated as a conditioning regimen for autologous stem cell transplantation (ASCT) in multiple myeloma (MM) patients with a prior transplant who had relapsed or achieved less than a complete remission following a prior ASCT. Thalidomide was dose escalated starting from 600 mg to 1000 mg on days -5 to -1 in a 3 × 3 design, bortezomib was administered at 1.6 mg/m² intravenously on days -4 and -1 and melphalan 200 mg/m² was administered on day -2. No dose-limiting toxicity was seen in the phase I portion of the trial. An additional 20 patients were enrolled at the maximum tolerated dose of thalidomide of 1000 mg daily. The overall response rate was 69% with 38% complete remission. Median PFS and OS were 9.3 and 65.4 months, respectively, with a median follow-up of 17.8 months. The most common grade 3-4 adverse events (AEs) were neutropenic fever (58.6%), mucositis (6.9%), and diarrhea (6.9%). Serious AEs included somnolence (13.8%) and tumor lysis syndrome (3.4%). The addition of high-dose thalidomide to bortezomib and melphalan as conditioning for salvage ASCT was well tolerated and was an effective conditioning regimen.